The invention relates in general to a pressure valve for use in fuel injection system of a motor vehicle, and in particular, to a pressure valve of the type which includes a connecting adapter or socket arranged between a work space of a fuel injection pump and an injection valve of an internal combustion engine.
A pressure valve of this kind has been described in German publication No. 3,112,100. This known pressure valve includes a disc or plate acting as a valve closing member, the disc being provided with an annular web acting as a valve seat which abuts against a plate shaped valve body. During the supply of fuel the valve closing member separates the pump side of the supply conduit from the injection valve. The valve closing member moves against the force of a resetting spring by a distance which when multiplied by the area of the valve closing member determines the volume of injected fuel less the volume flowing on the circumference of the valve body. During the injection interruption the valve closing member by the action of the resetting spring returns gradually to its seat on the valve body whereby the volume of fuel expelled during this return movement flows partially through a throttling passage which is formed between the valve body and the wall of the closing member.
The disc-shaped valve closing member of this kind however, has the disadvantage that it slants easily and under circumstances it can be become clamped. Moreover, there may occur also an irregular impact of the annular web on the valve seat formed by the valve body, especially when the valve closing member is not exactly guided in the radial plane. Furthermore, the prior art valve does not guarantee that after completion of the fuel supply the corresponding fuel injection valve is not momentarily opened by pressure waves reflected between the pressure valve and the injection valve. In this manner an undesired additional injection of fuel may occur. Provided that the cross-section of the throttling area on the valve closing member is made so large that the pressure waves are quickly neutralized, it may still happen that the static pressure before the actual closing of the pressure valve drops to such an extent that exhaust gases from the combustion space of the engine may penetrate in the fuel injection system.